Although a very considerable mass of evidence is now accumulating, we know considerably less of the brains of criminals than of their skulls. This is in large measure due to the fact that there is at present insufficient evidence regarding the condition of the normal and healthy brain, and unless controlled by careful series of observations on normal persons, observations on criminal brains cannot be interpreted. The important matter of the vascular supply of the brain in criminals has yet received little attention, but a variety of pathological features have been found in the cerebral substance and membranes--pigmentation, degenerating capillaries, cysts, thickened and adherent membranes, the vestiges of old hyperæmia and hæmorrhages. Some of these conditions are found with great frequency, much oftener than in the insane; meningitis, for instance, being found, according to Lombroso’s experience, in 50 per cent. of the cases examined; while Flesch has obtained very similar results. The frequency of meningitis was noticed in some of the answers to my Questions, especially by one prison surgeon who wrote of “well-organised adhesions between the dura mater and vault of cranium, localised but more extensive than one would expect to find.” Unfortunately, he was unable to supply exact figures as to the frequency of such signs. It must be added, as a point of considerable importance, that in very few cases have these pathological lesions produced any traceable symptoms during life. § 2. _The Face._ Prognathism has frequently been noted as a prominent characteristic of the criminal face, both in men and women. This is, however, a point that requires further study; giving due weight to racial characteristics, to the proportion of prognathous individuals among the general population, and to method and uniformity in measurement. There is little doubt that the lower jaw is often remarkably well developed in those guilty of crimes of violence. The squareness and prominence of the jaw are obvious to the eye, and this is verified by weighing after death, as has been shown by Manouvrier. The average weight of the Parisian criminal skull is, if anything, below that of the ordinary Parisian, but while the average weight of the lower jaw in the latter is about 80 grammes, it is about 94 grammes among murderers. In this respect the criminal resembles the savage and the prehistoric man; among the insane the jaw weighs rather less than the normal average. A type of receding chin is also found frequently among petty criminals, the occasional or habitual, who are criminals by weakness; such heads Lauvergne called _têtes moutonnes_.